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Meaning of plasmasphere

plas•ma•sphere

Pronunciation: (plaz'mu-sfēr"), [key]
— n. Astron.
  1. a region of cool plasma surrounding the earth, extending 8000–25,000 mi. (13,000–40,000 km) into space, and bounded by the plasmapause.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.